OK, I admit I've overfilled my new Prius twice. Both due to the pump nossle not shutting off (different stations in different cities). I usually add a little after shutoff but stop if I hear fuel at the bottom of the fill tube.

It is possible to damage the fuel tank in a Prius if you overfill - the fuel will expand into the evaporative canister and fill it, overflowing into the tank between the bladder and the steel. This fuel will "corrode" the fuel lines etc. It's about $1000 for a new tank.

So I did a quick calculation, based on .1% expansion per deg C for gasoline, fuel from underground tank at 15 C, air temp at 30 C. Looks like around 0.5 to 1.0 litre expansion. Add in the trapped air in the tank (yes, even with a bladder there will be some). It will expand more than the fuel.

Then I did a quick calculation of how much extra fuel you can put in if you overfill. It appears I went an extra 80-100 km on the two occasions I overfilled. This calculates to 4-5 litres of fuel between "normal" nossle shutoff and fill to top of filler tube.

Doesn't appear to be worth the risk!

 

I feel Toyota should cover the cost for any damage due to overfilling. Is it the customers fault they can't incorporate anti-overfilling technology into the car? We should be able to take care of the vehicle just like any other "Normal" vehicle. I am getting kind of pissed at the Prius design right now anyway. I have been very light footed driving mine and I can only average around 40mpg with 2800 miles on the car. I could have bought another vehicle that gets that mileage for half the cost.

 

Owch! What is your typical driving profile? Where are you located?

Bob Wilson

 

California

 

I only get about 45.6MPG after 1600 miles, in Texas.
But again, my per trip only takes less than 15 minutes most of time.
More than usual this week, I have to make the trip with each drive time in less than 6 minutes just simply because I have to drive across the toll way where there is no pavement available........Just today, Woody's MPG sinks all the way down to 42......

 

There are parts of northern California that are pretty chilly even during the summer. If that also includes a lot of short trips and/or hills without a chance to warm-up the ICE, you're a prime candidate for a block heater. Our Prius is sensitive to cold and the overhead of warm-up. Tacking on a mile or so at 25 mph at the beginning and end of a regular commute can do a lot to improve mileage.

The other risk factor is high speeds, especially without a chance to warm-up the ICE. By high speeds, we're talking +75 mph.

Your signature indicate you may have or had an Insight. What sort of performance did you get with that vehicle in the same driving?

I went to both the "Prius II" and "Insight" databases and didn't find a vehicle record for "resist." Recorded mileage is a great way to share what is going on.

Bob Wilson

 

wow that was quick! Must be the pumps up there haha. I've never overfilled or had fuel splurge out of the filler nozzle before.

 

Plenty warm on the Central coast of California. I used to own a CVT Insight and it got much better mileage than this Prius. Sure it was a much lighter vehicle with only 3 cylinders though.

 

That would be around LA? Even in warm weather, the warm-up of a Prius without a block heater is important. How about going over the FAQ and giving some ideas of what you're doing and what seems impractical?

Also, I'd like to suggest recording your mileage. Over time, this gives a better understanding of your driving profile. Understand that I'm less interested in "magic driving" than trying to make sure we're on the same page about the Prius performance characteristics.

Bob Wilson

 

Not LA, but the same temps. I drive 7 miles to work each day and 7 miles home. Mostly hilly roads.